Figure 3

(a) Image of the fabricated Bi–In–Sn MAE after the micromolding process. The sharpness of the needle tip is around 72 μm when it is fabricated under atmospheric pressure, as shown in the magnified image. (b) After fabricating MAE in a vacuum environment, the sharpness of the needle tip decreases to below 10 μm. (c) Image of Bi–In–Sn MAE before PUA coating, along with its magnified SEM image. (d) Image of Bi–In–Sn MAE after PUA coating, along with its magnified SEM image.